The present invention relates generally to the processing of refuse and other waste materials and more particularly, to an apparatus for shredding and compacting refuse.
Many types of apparatus for processing garbage, trash and other refuse are known in the art and which function to comminute the waste material and then compact it to reduce its volume so as to form plugs of highly compacted refuse which may be conveniently collected and handled. The older apparatus of this type usually employed a reduction mill or pulverizer for comminuting the waste material after which the material was fed through a feed chute to a compactor. The major disadvantages of such apparatus are their relative complexity and large size coupled with high manufacturing and maintenance costs. As the demand for simpler and less expensive apparatus increased, the older apparatus gave way to a new generation of combined shredder-compactor apparatus.
One such shredder-compactor apparatus which has proven highly successful in the field is the auger screw type. The auger screw type apparatus employs a rotary helical screw mounted within a housing which normally has a hopper and a compaction tube such that the waste material is received and shredded in the hopper and delivered to the compaction tube wherein it is compacted. The helical auger screw extends through both the hopper and compaction tube and is constructed so that the angular friction with respect to the refuse material is such that the screw effects compaction and reduction in volume of the comminuted material during its passage through the apparatus. As the auger screw rotates, it captures the refuse in the hopper and coacts with means located in the hopper to shred, shear and comminute the refuse and force the same into the compaction tube wherein the auger screw compacts and discharges the refuse in the form of highly densified plugs.
As a consequence of the large demand for shredder-compactor apparatus, much time and expense has been devoted toward improving the apparatus so as to simplify its installation, lower its price, make it more easy to operate and minimize its maintenance. Despite these objectives and notwithstanding the many improvements which have been made to date, the shredder-compactor apparatus which are currently available suffer several drawbacks. One drawback is that the auger screw wears very rapidly, especially if used with glass refuse. One approach taken to solve this problem was to harden the auger screw and though this successfully prolonged the life of the screw, it caused rapid wearing and deterioration of the compaction tube.
Another drawback is that certain refuse, such as cloth, fabric, and large plastic sheets, tend to move outwardly toward the crown of the auger screw and cling onto the screw so that they rotate with the screw rather than advance axially through the compaction tube thereby creating blockages in the compaction tube. In order to solve this problem, it has been proposed to form axial slots in the compaction tube so as to break up the clinging action of the material and cause it to advance lengthwise along the tube. Unfortunately, the slots quickly become clogged with refuse thereby losing their effectiveness and therefore removable cover plates had to be provided to gain access to the slots for maintenance purposes. However, each time the cover plates are removed and replaced, the seal around the slots beomes less effective and invariably waste material beings to ooze out beneath the cover plates.
Another drawback of the prior art shredder-compactor apparatus is that of maintaining sufficient back-pressure at the discharge end of the compaction tube to enable high density compaction to occur. If the back-pressure is too low, the material is not adequately compacted whereas if the back-pressure is too high, the material compacts too much and becomes so dense that overheating occurs which causes the material to adhere to the walls of the compaction tube. The devices currently employed to control the back-pressure, for the most part, are complex and expensive and unreliable in operation.
A further drawback of the currently available shredder-compactor apparatus is that the material tends to jam in the apparatus, especially near the discharge end of the compaction tube. Though automatic equipment has been added to automatically shut down the apparatus in this event, no practical solution has been devised to prevent jamming of the material or of relieving material blockages.